Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
At seismic acceleration within the range of 0,26 < PGA ≤ 0,36g surely the upper part of
ventilation stack of the special building SB2 will destruct. At its destruction the top one the third of
the chimney (about 50 m) may affect partially the neighbouring site infrastructure (ways) that will
cause difficulties in accessing SFS via these ways for the emergency teams or heavy machinery.
In the considered range of seismic acceleration, the SFS maintains capability to perform its
functions of safe storage of the spent fuel.
Analyses of „Off-site flooding” show that even volley discharge of entire volume of
Shimamov val dam cannot increase water level in the valley in vicinity of the plant more than
elevation +29.00, therefore there is no hazard of flooding at the site and direct impact on safety
functions. At assessment of response capabilities, it is required to consider possible flooding of the
part of Kozloduy town and correspondingly possible difficulties in accessing the plant.
All scenarios of combination of the beyond design basis earthquake with flooding lead to
loss of ShPS due to flooding. With their loss emergency make-up of the spray pools of Units 5 and
6 is also lost, i.e. time for ensuring of ultimate heat sink will be limited.
More important weaknesses were found at studying of flooding of the plant with MWL =
32,93 m, and may be divided as follows:
· termination to electric production and transfer of electric power supply sources to
DGS – due to possible loss of the part of electric lines, connecting Kozloduy NPP with the
power grid;
· termination to water supply in cold channel - loss of BPS and unavailability of access
to the BPS overland;
· loss of emergency make-up of the spray pools of unit 5 and 6– loss of shaft pump
station (ShPS);
· flooding of the part of town infrastructure and access from Kozloduy town to the
plant via bypass way.
· flooding of the part of underground communications below elevation 32,93 m –
drainage of the rainwater sewerage and leaks in its channels.
Potential external impacst due to flooding including failure to personnel access, equipment
and material delivery to the site are discussed in item 3.2.4. of this report.
6.1.3.1.2 Loss of communication structures/systems
At complete loss of power supply to the plant, margin for restoration of the power supply to
communication structures/systems is as follows:
· Availability of these systems from the UPS up 8 hours;
· Availability of these systems from DG-1 and DG-2 in AMC, more than 4 days.
6.1.3.1.3 Impact on various buildings and premises which are used by the crisis teams or to
which access will be required for accident management
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